The potential of biogas (with and without H 2 S) and volatile fatty acids (VFAs) to support microbial growth and accumulation of polyhydroxyalkanoates (PHAs) in type II methanotrophs was evaluated batchwise under aerobic conditions. Methylocystis hirsuta was able to grow on artificial biogas (70 % CH 4 , 29.5 % CO 2 , 0.5 % H 2 S) and accumulate PHA up to 45 ± 1 % (wt %) under N-limited conditions. The presence of CO 2 and H 2 S did not significantly influence the growth and PHA synthesis in M. hirsuta compared to control tests provided with pure CH 4 at similar concentrations. Likewise, *Revised Manuscript (clean for typesetting) Click here to view linked References the addition of VFAs to the cultivation broth at initial concentrations of 100-200 mg L-1 did not hamper the growth of this strain on artificial biogas. Indeed, the addition of 10 % extra carbon in the form of individual VFAs resulted in an increase in the maximum PHA yield and final PHA content up to 0.45-0.63 gPHA gSubstrate-1 and 48-54 % (wt %), respectively, at the expense of a higher energy demand. Valeric acid supplementation supported the highest 3-hydroxyvalerate content (13.5 %) within the biocomposite. In this context, this study demonstrated for the first time that 3hydroxyvalerate synthesis by M. hirsuta did not depend on CH 4 assimilation.

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The supercritical fluid extraction (SFE) and fractionation of lipids from broccoli leaves is presented in this work. For this purpose the effect of the different variables on the extraction was studied, obtaining the best results at 608C, 300 bar and 3 mL/min. Two different fractions were obtained: First, the samples were extracted with pure CO 2 , and afterward the residual material was extracted using CO 2 modified with 15% of methanol. The total fatty acid content of the extracts was determined by GC-MS and compared with those results obtained by Soxhlet extraction with hexane and a chloroform/methanol (2:1) mixture. The SFE extracts presented a higher percentage of unsaturated fatty acids, especially the polyunsaturated 18:3 n À 3. The methodology was successfully applied to the analysis of the fatty acid composition of the leaves from five different cultivars of broccoli. In all the samples the main fatty acids were a-linolenic (18:3 n À 3), linoleic (18:2 n À 6), and palmitic (16:0). Among the different cultivars analyzed, Naxos variety presented the highest levels in fatty acids, while Parthenon and Viola the lowest. Practical applications:The proposed method allows the fractionation of lipids from broccoli leaves using a small volume of organic solvent and mild conditions. This is advantageous compared to conventional methods where large volumes or organic solvents are used, and the cost and time for the removal of these solvents, along with the possibility of degradation and toxicity, are the major disadvantages. The results obtained contribute to a better compositional characterization and a possible revaluation of this by-product as a source of biologically active compounds.